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Date: Tue, 15 May 2001 15:49:31 -0700 (PDT)
From: James Simmons <jsimmons@transvirtual.com>
To: Chip Salzenberg <chip@valinux.com>
cc: Alan Cox <alan@lxorguk.ukuu.org.uk>,
        Linus Torvalds <torvalds@transmeta.com>,
        Neil Brown <neilb@cse.unsw.edu.au>,
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        "H. Peter Anvin" <hpa@transmeta.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        viro@math.psu.edu
Subject: Re: LANANA: To Pending Device Number Registrants
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> According to Alan Cox:
> > Given a file handle 'X' how do I find out what ioctl groups I should
> > apply to it.
> 
> Wouldn't it be better just to *try* ioctls and see which ones work and
> which ones don't?

You can do this with the tty layer. Just open /dev/tty and try tioclinux. 
On my serial console it fails and when I run the exact same program works
on my VT. It is the only way to see if these ioctl calls work. No other
way to see if your on a serial console or a VT.